Cathode ray tube structure



April 12, 1960 P. HAAS CATHODE RAY TUBE STRUCTURE Filed Nov. 16. 1955 INVENTOR /UL HAAS 722mm .0772

ATTORNEY United States Patent O CATHODE RAY TUBE STRUCTURE Paul Haas, Seneca Falls, N.Y., assignor, by mesne assignments, to Sylvania Electric Products Inc., Wilmington, Del., a corporation of Delaware Application November 16, 1955, Serial No. 547,136

1 Claim. (CI. 95-1) This invention relates to a support structure and more particularly to a structure for supporting and positioning a mask with respect to a printing device and the viewing panel of a cathode ray tube during the photoprinting process conventionally used to produce color television picture tubes.

In the processing of tri-color picture tubes, a pattern of blue, green, and red fluorescent phosphor dots or strips are conventionally formed on the inside surface of the picture tube face plate by means of a photo-printing technique. In accordance with one preferred technique, a first phosphor, which may be a blue iluorescent phosphor material, is combined with a photosensitive substance to form a layer of material which is deposited on the face plate of the tube. This layer is subjected to light rays for a predetermined period of time through a negative which may be the shadow mask employed in the tri-color dot type picture tube. Those areas of the phosphor and photosensitive composition layer which have been subjected to light become hardened and adhere to the face plate of the tube. A subsequent developing operation utilizing a washing step wherein the layer is rinsed with a suitable developing fluid completes formation of the blue fluorescent phosphor pattern. This process is then repeated for the green and red fluorescent phosphor pattern forming operations to complete the tri-color screen. The light source is indexed to a predetermined position for each of the dot forming operations in accordance with the electron excitation areas on the screen as determined by the three cathode emitters employed in the tube.

The printing negative or aperture mask assembly employed in the picture tubes described above conventionally comprise a perforated metallic mask or printing negative structure which has mounted about its periphery or on a stilfem'ng frame attached to its periphery an accurately formed positioning member. This member serves to align the mask with respect to the picture tube face plate on one side, and the light source housing on the other side. Presently used mask assemblies employ braces mounted on the periphery of the mask which have a central section and opposed end sections formed with grooves. The central section is welded to the edge of the mask so that the end sections are disposed in a spaced relationship above and below the mask. When the light source housing, aperture mask assembly, and picture tube face plate are in position for the exposure step of the pattern forming operation, the positioning pins of the housing are resting on the upper brace end section, while the lower end section of the brace is lying upon the glass nubbins or protrusions integral with the face plate of the tube. The weight on the brace from the light housing and frame has a tendency to set up a stress in the center section of the brace, and this stress is often Sullicient to cause the attached perforated mask to become deformed. Any such force on the mask results in a distortion of the mask aperture pattern causing a resulting error in the exposed phosphor pattern.

ICC

Accordingly, it is an object of the invention to reduce the aforementioned diiculties, and to provide a printing assembly which may be eiciently and accurately positioned with respect to the cooperating devices used in a pattern printing operation.

A further object is the provision of a printing assembly adaptable for automatic production.

A still further object is the provision of a cathode ray tube screen processing component assembly which provides means for producing a screen with minimum pattern distortion.

The aforementioned objects are achieved in one aspect of the invention by the provision of a mask assembly employing several brackets mounted upon or integral with the perforated mask. The brackets are formed to cooperate on one surface with the positioning pedestals of a radiant energy or light source frame, and with the picture tube face plate integral glass nubbins on the opposite surface. A construction of this type provides structural support areas selected so that no stress will be imparted to the mask assembly during the screen processing operation.

For a better understanding of the invention, reference is made to the following description taken in conjunction with the accompanying drawings in which:

Fig. l is a partially sectioned perspective View of the cooperating components employed in a cathode ray screen processing operation;

Fig. 2 is an enlarged section projected from the view shown in-Fig. l illustrating one aspect of the invention; and

Fig. 3 is an enlarged perspective view of the bracket constituting an element of one embodiment of the invention.

Referring to Fig. l, an aperture mask assembly 11 iS shown mounted between `.a cathode ray tube face plate assembly 13 having a panel 19 and light source frame 15 supporting a light box 17. rEhese structures are arranged in accordance with their assembled positions during the exposure period of the radiant energy or photoprinting process. In this process, a layer of a first phosphor such as the blue phosphor zinc sulfide, is deposited on screen panel i9 along with a photosensitive material such as polyvinyl alcohol sensitized with ammonium dichromate. Mask assembly 11 is then positioned above screen panel 19 and frame 15 is mounted in its appr0.

priate position upon mask assembly 11 and opposite screen panel 19. The layer of phosphor and photosensitive material deposited on the screen panel is then subjected to ultra violet light traveling from light box l? and through aperture mask assembly 11. Those areas of the screen panel which have been exposed become hardened and adhere to the glass panel. Frame 15 and aperture mask assembly 11 are then removed from face plate -assembly 13, and panel 19 is washed with a suitable rinsing fluid such as deionized water to effectively develop the blue iiuorescent phosphor pattern. The complete tri-color pattern is made by repeating the previous steps sequentially for the green fluorescent phosphor, zinc ortho-silicate, and the red fluorescent phosphor, zinc phosphate. The tri-color pattern of phosphor dots is attained byfindexing light box 17 so as to provide a pattern conforming to the excitation areas of the appropriate ones of the three cathode emitters employed.

in the tube.

Housing 15 comprises a rotatable plate 2.1, a skirt portion 23, and integral lugs 31. Plate 21, shown supported upon the upper portion of skirt 23 is provided with three apertures disposed apart. These apertures cooperate with removable dowel pins 29, so that the pins may be disengaged after each phosphor dot forming operation tube to facilitate rotation of light box 17 to its subsequent op` erational position. Although three pins 29 are shown, a single pin may be used or any other means for sequentially rotating plate 21 over 120 and locking it in position after each rotation such as a spring loaded ball and cooperating socket combination may be employed.

lPositioned on top of rotatable plate 21 is light box 17 which has mounted therein a light .-ernitter. The light from box 17 travels downwardly from plate 21, and through .the apertures in mask assembly 11. Cables 2S serve as the electrical connectors for the light emitters, and conduit 27 serves as a means for air-,cooling the area Within the box.

Skirt 23 is shown formed as a truncated cone type hoop having large elliptical perforations and stitening ribs. Attached along the periphery of skirt 23 are a plurality of lugs 31 which are integral with skirt 23 and oppositely disposed from pl-ate 21. Lugs 31 extend from skirt 23 along a plane normal to the axis of the skirt. kArranged inthe lugs are pins 33 which serve as positioning and locating means lfor frame with respect to mask assembly 11 and face plate structure 13.

The three positioning pins 33 are disposed around skirt 23 so that two of them are spaced less than 120 apart, with the third pin being located in the lug which is equidistant from the other two. This type of positioning provides an ethcient and accurate means for attaining repetitious placement since frame 15 will cooperate with mask assembly 11 and face plate structure 13 in only one manner. Also disposed in lugs 31 are rods 35, which serve to provide additional multi-point pressure upon the mask assembly 11 during the` phosphor pattern forming operation. Weights may be mounted upon the upper portions of the lugs cooperating with pins 35 if desired to reduce the possibility of the thin perforated mask assembly from being bent or warped during the printing oper-ation.

The ends of pins 33 have substantially V-shaped grooves formed therein for cooperation with brackets 39 mounted upon the aperture mask 12, The brackets in turn are positioned with respect to face plate panel 19 by means of integral glass nubbins 411. The mask therebyhas a three position support upon three nubbins arranged on the internal edge of face plate structure 13. Frame 1S also has a three point support by means ofthe cooperation between pins 33 and the brackets 39. ln addition, mask 12 rests upon a number of glass lands which have been provided intermediate nubbins d1 along the periphery of panel'19. Weighted rods, when used with pins 35, rest on the mask and thereby apply pressure to those points of the mask frame cooper-ating with the face plate'lands. lf desired, mask 11 may have attached thereto more than three brackets of the type designated at 39,

and frame 15 may have as many positioning pins 33 as is needed to effectively position and support the housing. In addition, mask material thickness, size of the mask assembly, and the number of perforations will determine the number of rods and the size of the 'weights or spring pressure devices which may be used to hold the mask assembly 11 in correct position with the face plate assem bly'13. Y l

`Referring to Figs. 2 and 3, bracket 39 comprises a central section 43 and end sections 45. The extremities of the end sections `are bent 90 to provide a surface which is secured to the aperture mask by any convenient means such as by welding. A cut-out portion ad in mask 12 allows pin 33 to have access to bracket39. Central section 43 is bent in the form of an inverted substantially V-shaped configuration, but any linear or curvilinear form may be employed so long as it is able to provide a means -for transferring the weight on pins 33 Yto nubbins 41 without creating a strain in the mask. The preferred embodiment shown in the drawings lenables a two-position contact to be made, one position being on either leg of section 43. The positions are defined by the opposing surfaces of glass protrusions 41 and positioning pins 33. Therefore, there is no opportunity to set up a strain in the bracket and attached aperture mask. A line drawn through the Contact positions designated at 47 will lie substantially normal to the plane of cach leg forming central section 43,

Bracket 39 is shown in Fig. 3 as being formed from a single strip of material. However, the bracket structure may be formed by pressing or otherwise forming it as part of the peripheral portions of mask 12, thereby providing an integral positioning member.

When mask assembly 111 is employed as an electrode in the completed picture tube, the mask is positioned upon face plate assembly 13 by means of brackets 39 and Although housing 15 has been shown with a rotatableplate 21, it may be advantageous to utilize three such housings, each with =a light box 17 permanently atxed in one of the three operational positions. In production, this housing would then be used continuously for only the appropriate one of the three phosphor exposure operations.

Mask assemblies made in accordance with the invention may be easily and accurately` positioned upon and removed from the face plate assembly during screen processing operations. ln'addition, the structure of the bracket shown and described provides an er'iective support for the mask without imparting a strain to the mask during the exposure process.

While there has been shown and described what at present is considered to be the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein Without departing `from the scope of the invention as defined by the appended claim.

What is claimed is:

A mask assembly adapted to be used in the production of a cathode ray tube in conjunction with a viewing panel having positioning means and a panel processing device having spaced contact surfaces comprising a mask formed in accordance with a predetermined pat-tern and a plurality of spaced brackets integral with said mask formed` to provide an index for orienting said mask, said view-V ing panel Vand the processing device relative to one another, said brackets having connected legs forming a substantially V-shaped section formed to abut said contact surfaces on one side and said positioning means on the opposed side at prescribed points which lie in a common plane substantially normal to the plane of'said legs.

References Cited in the le of this patent' UNITED STATES PATENTS 

